Ship control system



June 1965 H. L. SHATTO, JR.. ETAL 3,

SHIP CONTROL SYSTEM Filed March 14. 1961 3 Sheets-Sheet 1 s Y lsl R YFIG. 4

INVENTORSI H. L. SHATTO JR. J. R. DOZIER BYg mf THEIR ATTORNEY June 8,T965 Filed March 14, 1961 AZIMUTH ACTUATOR H- L. SHATTO, JR.. ET AL SHIPCONTROL SYSTEM FIG. 3

Y AXIS ACTUATOR THRUST CONTROLLER 3 Sheets-Sheet 5 ONTROLLER THRUST WIH. L. SHATTO JR J. R. DOZIER THEIR ATTORNEY United States Patent 03,187,704 SHlIlP CUNTRUL SYSTEM Howard L. Shatto, in, halos Verdes, andJames Ronald Dozier, Whittier, Califi, assignors to dhell Gil Company,New York, Niifl, a corporation of Delaware Filed Mar. 14, 1951, Ser. No.95,6llll Ill Qlaims. (ill. 114-444) This invention pertains to a noveldevice or system to anchor a marine vessel dynamically over a particularlocation on the floor of a body of water and to provide a vessel with ahigh degree of maneuverability.

In oifshore drilling operations it is desirable to be able to drill froma floating vessel which is merely maintained over the spot on the oceanfloor and is not required to be anchored or otherwise fastened to theocean floor. In the past, it has been the practice to either erect atower over the desired location and drill from a fixed platform on thetower or anchor a floating vessel over the spot and drill from theanchored vessel. In either case, the drilling platform or vessel hasbeen attached to or anchored to the ocean floor in order to maintain itin a fixed location. While these methods are satisfactory they haveseveral disadvantages. For example, the use of a fixed tower is limitedto rather shallow depths while the use of an anchored vessel requiresthe placement of suitable anchors in a plurality of directions tomaintain the vessel in position. The placement of these achors requiresa considerable amount of time which greatly increases the cost ofdrilling and is, of course, impossible in deep water.

In addition to drilling vessels many other vessels must be maintainedover a fixed spot or maneuvered in narrow channels. For example,oceanographic, weather, salvage and radar vessels must be maintained infixed locations. Similarly, fire boats and tugboats must be maneuveredin limited areas. Thus, while this invention is described below asapplied to a drilling vessel, it can be used to anchor dynamically anyvessel or to maneuver any type of vessel.

T he high cost of the prior methods of operation could be avoided if itwere possible to maintain a floating vessel over the desired drillingspot without the use of anchors or other fastening means. In such anoperation, it would only be necessary to move the drilling vessel to thedesired location and hold it in position while the drilling operation isperformed and then move on to the next spot. Such an operation wouldhave considerable advantage especially during the early stages ofoffshore operations when only shallow core wells are to be drilled.

Accordingly, it is the principal object of this invention to provide aunique method and apparatus for dynamically anchoring a vessel in adesired location and orientation or for providing a high degree ofvessel maneuverability.

A further object of this invention is to provide a novel controlapparatus for automatically positioning a vessel over a desired locationor maneuvering a vessel along a desired course.

A further object of this invention is to provide a novel method andapparatus by which an operator may manually position a single controldevice to maintain a vessel over a desired location or to maneuver thevessel over a desired course.

Another object of the present invention is to provide a vessel with aplurality of propulsion units having variable thrust and a vairabledirection of thrust through a full circle with a novel control systemwhich separately varies the magnitude of the thrust and its directionfor each of the units to maintain the vessel over a desired position orto maneuver the vessel over a desired course.

A still further object of the present invention is to provitle a vesselhaving a plurality of propulsion units with an automatic system forvarying the thrust and direction of thrust of the propulsion units tomaintain the floating vessel over a desired position.

A still further object of the present invention is to provide a uniquecontrol system for controlling the magnitude of the thrust and thedirection of thrust of a plurality of propulsion units displaced fromthe center of rotation of a vessel to maintain the vessel over a desiredposition. The control system utilizes information indicating themeasured horizontal position of the vessel to compare with the desiredposition as well as the measured heading of the vessel to compare withthe desired heading to provide signals for controlling the magnitude ofthe thrust and the direction of the thrust of the propulsion units.

A still further object of this invention is to provide a novel controlsystem for controlling the magnitude of the thrust and direction of thethrust of a plurality of propulsion units displaced from the center ofrotation of the vessel to maintain the vessel over a desired position ormaneuver the vessel along a desired course. The control system utilizesa vector resolving unit which provides for the gang operation of thepropulsion units to provide substantially parallel thrust vectors toobtain a resultant horizontal thrust vector and to modify the individualthrust vector of each propulsion unit by the vector addition ofrotational vectors substantially tangential to the circumference of acircle drawn through each propulsion unit about the center of rotationof the vessel.

A still further object of this invention is to provide a vectorresolving unit that accepts command signals indicating desired resultantnet horizontal and rotational thrust to be provided to the vessel.

A still further object of this invention is to provide a vectorresolving unit that accepts command signals from a single natural andcomprehensible manual control to provide a high degree of manualmaneuverability for a vessel.

A still further object of this invention is to provide a vectorresolving unit that accepts command signals from automatic controllersthat indicate the desired movement of vessel in two directions at anangle to each other and the desired rotation of a vessel.

The above objects and advantages of this invention are achieved byproviding multiple propulsion units mounted on a vessel and displacedfrom its center of rotation. Each propulsion unit is provided with ameans for varying the magnitude of its thrust as well as the directionof the thrust in much the same manner as one varies the magnitude ordirection of thrust of an outboard motor. A means is provided fordetermining the horizontal or angular displacement of the vessel fromits desired location, such as the use of visual or electronic inspectionof reference points, mechanical or electrical measurements ofdisplacement from a desired location, and a compass heading. Theseposition signals are compared either manually or by automaticcontrollers with the desired position, and corrective command signalsare sent to the vector resolving unit. The vector resolving unitprovides gang operation of the propulsion units to provide parallelthrust vectors to obtain a resultant horizontal thrust vector and tomodify the individual thrust vector of each propulsion unit by vectoraddition of a rotational vector.

In order to prevent the control system from frequent radical changes inthe direction of the thrust of the propulsion units when the propulsionunits are operating at near zero magnitude of thrust, it is desirable toprovide a diiferential bias system which results in a bias vector foreach propulsion unit, the vector sum of all the individual bias vectorsbeing equal to zero.

From the description, it is clear that the control system of thisinvention permits most efiicient use of the propulsion units withminimum interference between various L. desired corrective actions. Forexample, the vessel may be rotated about its rotational axis Withoutrequiring additional corrective actions to eliminate the erroneousinterje'ction of translation vectors. Similarly, the vessel may betranslated without requiring corrective action to prevent rotation.

The above objects and advantages of this invention will be more easilyunderstood from the following detailed description when taken inconjunction with the attached drawings, in which:

FIGURE 1 is a schematic representation showing the location of the twopropulsion units on the floating vessel and a means for determining itsdisplacement from a desired position;

FIGURE 2 is a block diagram illustrating one embodiment of the controlsystem of this invention;

FIGURE 3 is a pictorial representation oi a mechanical vector resolvingunit which permits either manual or automatic control of a vessel; and,

FIGURE 4 is a vector diagram illustrating the vector resolving for thebow and stern propulsion units.

Referring to FIGURE 1, there is shown a vessel 14? having a propulsionunit :11 located at its stern and a second propulsion unit '12 locatedat its bow. The two propulsion units are located along the central axisof the vessel and each rotates about a vertical axis intersecting thisaxis. Each of the propulsion units is provided with a means torindividually varying their direction of thrust as well as the magnitudeof their thrust. Suitable units are electrically driven outboard motortypeunits in which the speed of rotation of the propellers may be variedto vary the thrust supplied and the complete unit rotated about avertical axis to vary the direction of thrust.

Also shown in FIGURE 1 is a method for utilizing a taut guide line 13 todetermine the displacement of the vessel from its desired location. Theguide line 13 is connected to the vessel 19 at its upper end and to ananchor 14 at its lower end with the anchor 14 being disposed at thedesired location of the vessel. The angular deflection of the guide linefrom the vertical is measured in two vertical planes at right angles toeach other as indicated by the angles x and y in FIGURE 1. Thedeflection of the guide line may be measured by various means, forexample, a pair of potentiometers 15 and 16 disposed at right angles toeach other and operated by a gimbal mounted pendulum 17. A tiltmeter ofthis general construction and suitable for measuring the angulardeflection of a taut line is disclosed and claimed in a copendingapplication of Kenneth Foster, Serial No. 830,604, filed July 30, 1959.

In addition to measuring the angulardisplacement of the vessel from itsdesired location the compass heading of the vessel is determined. This,oi course, may be accompli-shed by any known type of compass butpreferably a gyrocompass is used in order to obtain an electrical signalwhich is related to the compass heading.

Referring to FIGURE 2, there is shown a block diagram of one embodimentof this invention. Two propulsion units 11 and 12 are disposed at thebow and stern of the floating vessel, respectively. The disposition ofthe propulsion units is shown in FIGURE 1 in which the units areillustrated as being disposed in wells formed in the bow and stern ofthe vessel '10, respectively. The propulsion units are provided with athrust generating means such as propellers 20 and 21 driven by avariable speed drive means, i'or example an electric motor of theinduction type coupled to the propeller-s through eddy current couplings22 and 23. Similarly, the propulsion units may be rotated about theirvertical axes 24 and 2,5

degrees. Several types of propulsion units fulfilling these requirementsare available.

The propulsion units are provided with synchro-transmitters 2d and 27which provide a signal indicating the direction of thrust of thepropulsion unit relative to the vessel. The synchro-transmitters 26 and27 are coupled to synchro-receivers 3b and 31, respectively, by means ofcircuits 32 and $3. The synchro-receivers 3t and 31 form a part of thevector resolving unit 3d which receives information irorn varioussources and provides signals for controlling the stern and bowpropulsion units. The vector resolving unit 3 1- will be described ingreater detail below.

The vector resolving uni-t 34- provides four signals which areschematically illustrated by the lines 35, 3d, 37 and 33. The lines 35and 3% represent control signals suitable for controlling the thrust ofthe propulsion units. These lines are shown as being connected to eddycurrent couplings Z2 and 23 of the propulsion units ill and T12,respectively. The lines 36 and 37 represent signals which are used tocontrol the direction of the thrust of the two propulsion units 11 and12, respectively. The signals represented by the lines 36 and 37 aresupplied to the steering motor reversing starters db and 411 which inturn start, stop and reverse the steering motors 4-2 and 4-3,respectively.

The vector resolving unit 34 receives signals representing the desiredthrust to be supplied in the x and y planes as well as the rotationalthrust required of the propulsion units. The desired thrust in the x andy planes is determined by controllers 44 and 45. Each of thesecontrollers receives a separate signal from the tiltmeter potentiometers4d and. 4'7 which measure deflections in the vertical planes disposed atright angles as explained above. The controllers 44 and 435 can becommercial controllers that have, in addition to set point adjustmentsEitl and 51, conventional control response adjustments such asproportional, reset and derivative actions. In addition, the con-.troller it is supplied with an input 59 which supplies ananti-oscillation vector as described more fully below. The rotationalcontroller 52 receives a signal from gyrocompass 53 and is similar tocontrollers t4, and 45' in its actions.

The vector resolver can also receive signals from a single manual input5 The manual input provides three output signals comparable to thosesupplied by controllers id, 45 and 52. In addition, the manualcontroller has a handle 55 which may .be moved by an operator in thedirection in which he desires the vessel to move or rotate the handle torotate the ship Without a change in horizontal thrust vector. Both themanual control 54 and the controllers 44, 45 and 52 supply signalsillustrated by the lines 56, 57 and 58 which are vectorially combined inthe vector resolving unit 34. A three-pole switch 60 is provided forcoupling either the controllers 44, 45 and 52 or the manual controller54 to the resolver 34.

From the above discussion it can be appreciated that means have beenprovided by which two propulsion units located in the bow and stern ofthe vessel may be positioned in order to maintain the vessel over itsdesired position or move it along a desired course. The propulsion unitsare provided with a variable thrust means as well as a means for varyingthe direction of the thrust in order that the vessel may be maintainedover its desired location or moved over a course. The vector resolvingunit 3 provides signals for controlling both the magnitude of the thrustsupplied by each of the propulsion units as Well as the direction of thethrust. In order to provide the required control signals the vectorresolving unit receives signals indicating the direction in which eachof the propulsion units must be directed and the thrust required of eachunit to move the vessel back to its desired location.

Referring now to FIGURE 3, there is shown an electromechanicalcontroller for performing the operations of the vector resolving unit 34described above. The

vector resolving unit consists of the two synchro-receivers 3t and 31described above which drive potential disks 7% and 71. Each of thesynchro-receivers drives a similar potential disk and only the onerelated to the receivcr will be described in detail. Thesynchro-receiver 30 has a rotating shaft 72 which is connected to thepotential disk 70. The disk is divided into two halves 73 and 7 by meansof insulating strips 75' and 76 with the insulating strip 75 being ofrelatively narrow width while insulating strip 76 is of more substantialwidth. The exact width of the two insulating stri s 75 and 76 may vary,the only requirement being that the pick-up or brush 77 described belowshould bridge the strip 75 but fail to bridge the strip or. Thus, whenthe pick-up means 77 is disposed along insulating strip 76 no currentwill flow through the lead Slit connected there to. The lead 8?] iscoupled to a power supply 03. K to one side of a series of relay coils82, 83, 84 and 8:.

The pick-up of the disk 71 is coupled in parallel with the pick-up 77 byleads 86 and S7. The leads 90 and 91 from the halves 73 and 74 of thepotential disk 79 are coupled to the other ends of the relay coils 82and 83. The leads from the two halves of the potential disk 73. aresimilarly coupled to the other ends of relay coils 84 and 85. The relaycoils 8235 operate relay contacts 92-95, respectively, to control tieflow of current from a source ltlt through the coils 96-99.

The relay contacts I and 93 operate the coils, Q6 and 97 respectively,in the steering motor reversing starter on which causes the steeringmotor to rotate either counterclockwise or clockwise. in a like manner,the contacts 94 and 95 operate the coils, 93 and 99 respectively, in thesteering motor reversing starter 41 which causes the steering motor 43to rotate either counterclockwise or clockwis Disposed in series withthe relay coils and are normally closed contacts ill-1 and which areoperated by the relay coils 32 and Ed, respectively.

In order to best understand the operation of the potential disk pick-upcombination, only the operation of the disk 79 and pick-up 77 will bedescribed. As the pick-up 77 is moved from the wide insulatim strip 76it will cause the relay coil 82 or 83 to be energized depending intowhich half of the disk 70 the pick-u is moved. To prevent an ambiguityas the pick-up is moved over the narrow insulating strip 75 the normallyclosed contacts 1-71 are inserted in series with the coil 83 andoperated by the coil 82. Thus, the contacts it'll will remain closed asthe pick-up passes from the half 74 until the pick-up makes contact withthe half 75 at which time the contacts lit-l will open. It can also beseen from the above description that when the pick-up is in contact withthe half 74 the relay coil 83 will be energized to close contact 93,thus energizing the starter coil 97 from source 180. Relay coil 82 issimilarly energized when the pick-up is in contact with half 73 to closecontacts 92 and energize coil 96. Of course, coil 95 should causerotation of the steering motor 4?; in one direction while coil 97energizes the steering motor 42 to rotate in the opposite direction.ciated with the potential disk 71 cause the steering motor 43 to operatein the same manner.

From the above discussion it is apprec ated that if the pick-up 77 ismoved in the direction that one wishes the stern propulsion unit to bedirected the circuits will cause the steering motor 42 to rotate thepropulsion unit to this direction. The steering motor 42 will rotate thepropulsion unit until the wide insulating strip 76 of the potential diskis again aligned with the pick-up. The potential disk is, of course,rotated by the synchro-transmitter receiver combination 26 and 34 Inorder to provide a means for changing the thrust of the propulsion unita displacement type actuator N3 is used. The actuator 163 is coupled tothe pick-up 77 by means The circuits asso- U iii of a flexible cable resthat passes through a bushing 1% located at the central axis of the disk7t). Thus, the farther the pick-up 77 is moved from the center of thedisk 7% the greater will be the thrust supplied by the propulsion unit.

The single potential disk 79 provides a means for resolving thedisplacement of the pick-up 77 in two directions to obtain the desireddirection of the propulsion unit and the desired thrust of thepropulsion unit. Of course, the potential disk 71 will similarly resolvethe displacement of its associated pick-up to control the direction andthrust of the bow propulsion unit 12. It is thus easily seen that if thepick-ups associated with the potential disks 7% and 71 were moved inunison that the vessel ll of FIGURE 1 could be moved longitudinally,laterally or merely rotated about its center of rotation.

In order to move the pick-ups in unison the pick-up '77 is attached toan arm member 116 which extends outwardly from a channel-shaped supportill. The arm member and support All are disposed for sliding movement ina slot 11?. formed in one of the flanges of a channel-shaped base 113.The pick-up associated with the disk 73 is connected to a similar armlid attached to a channel-shaped support 115. The arm 114 is alsodisposed for sliding movement in a slot 116 formed in the other flangeof the channel-shaped base 113.

A rack member ill? is formed on or attached to the surface of thesupport opposite the surface to which the arm H4 is attached with asimilar rack being disposed on the support 111. A pinion member 12h isdisposed between the ack H7 and the second rack mounted on the supportall. The pinion 129 is held in position by which extend out over therack 117 and similar flanges formed on the support iii.

A rotational actuator 1211 which is controlled by the signal 56 ofFIGURE 2 is secured to the bracket 11 The actuator 121 must be anactuator which may be controlled by the signal 56 or the signal must beconverted. For example, in the case or" a hydraulic actuator and anelectrical signal, the signal would have to be converted before theycould be used to control the movement of the actuator. The piston rod122 of the actuator 123 is coupled to an arm 123 by means of a pin withthe arm 123 being secured to the support 115.

From the above description it can be appreciated that as the piston rodof the actuator 12d reciprocates, it will cause the rack 117 and supportto move longitudinally along the face of the flange on thechannel-shaped base 113. As the support 115 moves in one direction thesupport 11.1 will move in the opposite direction. Thus, the pick-up 77and the pick-up associated with the poten- 1211 disk 71 will move inopposite directions across the race of the two potential disks.

The y actuator 13!? is rigidly secured to the bottom of thechannel-shaped base llllli. The piston rod 131 of the actuator 13% isrotatably connected to a shaft 132 which extends upwardly from thepinion 120. Thus, as the piston rod 131 of the actuator reciprocates itmoves the pinion 122i) and the two racks as a unit in a directionparallel to the axis of the base 113. The y actuator 139 is positionedby the signal 58 of FIGURE 2 and it may be necessary to convert thesignal 58 to operate the actuator 139.

The x actuator 140 is fastened to a way 141 which supports one end ofthe base 113, with the other end of the base being supported in asimilar manner by a way 142. The piston rod 143 of the actuator 14% irigidly secured to the supporting base 113, thus as the piston rod movesit will move the supporting base 113 along the ways 141 and 14-12. Thismovement will cause the pickups associated with the potential disk tomove in unison in a direction at right angles to the movement of thepick-ups by the actuator lldti.

The shaft 132 which extends from the pinion 12b is used as a manualcontrol since it may be used to move the two pick-ups in two directionsat right angles to each other and to move them in opposite directions.The first two movements are obtained by moving the shaft 152 in thedesired directions while the last movement is obtained by rotating theshaft 132. Of course, it is necessary to inactivate the actuators 1'21,139 and when the pick-ups are manually positioned.

in addition to the above-described method for ellecting manual controlof the propulsion units, one could use the system shown in FIGURE 2 incombination with the vector resolver shown in FTGURE 3. "if the systemof FEGURE 2 is to be combined with the system shown in FEGURE 3, themanual control device 54 should consist of a series of threepotentiometer-s for supplying electric signals such as would be suppliedto the controllers 4d, 45 and 52. These potentiometers would all beoperated by a single control handle '55 which could be moved thedirection in which it wa desired to move the vessel and rotated torotate the vessel with substantially no translation movement. Thecontrol handle 55 moves two potentiometers disposed at right angles toeach other to supply the x and y signals and when rotated it positions athird potentiometer to supply a rotational signal. The three signalssupplied from the manual control are supplied to the actuators T121, 13$and Mil in the same manner as the signals from the controllers 4 5 and52 are supplied. Thus, the manual control provides an easy means bywhich one can exert manual control over the system to direct the vesselalong a desired course or maintain it dynamically anchored over a fixedposition.

When the two propulsion units are run at substantially zero speed thevector resolving unit of FlGURE 3 will i call for frequent and largerotational movements of the propulsion units in order to maintain thevessel dynamically anchored over the fixed position. in order to preventthese frequent and large rotation of the propulsion units a turn bucklearrangement is provided on the vector resolver. The turn buckle consistsof a threaded tubular member and two threaded shafts 151 and 152. Thethreaded shafts thread into the tubular member 15% and are securelyattached to the two synchroreceiving units 13 9 and 131. A groove 153 isformed in the center of the tubular member 159 with a support member 154being disposed to engage the groove. Thus, when the tubular member isrotated it will move the synchro-receiving units 139 and 131 closer orfarther apart. As the pick-ups for the two potential disks ill and 71are displaced from the center of the disks by the turn bucklearrangement they will cause the units to rotate at slow speeds whilefacing in opposite directions. This will introduce a biasing oranti-oscillation effect to the system and prevent the frequent and largerotational changes described above.

in order to both understand the operation of the vector resolving unit,reference is now made to FIGURE 4 showing a two vector diagram res and161. The vector diagram res shows the vector resolution for the sternpropulsion unit Ill while the diagram loll illustrates the vectorresolution for the bow propulsion unit 12. in both of the vectordiagrams the vectors x and represent the signals supplied by the x andcontrollers 4-4 and of FTGURE 2. As explained above, these controllersreceive signals from a tiltmeter which are related to the displacementof the vessel from its desired location. The signals are the anglebetween a taut line and the vertical in two planes at an angle to eachother. The controllers compare the signals received from the tiltmeterwith preset values supply related signals to the vector resolving unit.In addition, the controllers should be capable of supplying a derivativeor proportional action in order that they may prevent the control systemfrom over correcting and thus hunting or oscillating. The term orepresents the signal supplied by the rotation of controller 52.

This vector is proportional to the rotational force required to returnthe vessel to its required heading. As shown in PiGUllE 4-, the x and yvectors are added by the resolving unit of FTGURE 3 while the rotationalvectors 4) are added for one propulsion unit and subtracted for theother. This, of course, provides for the most eilicient use of thepropulsion eliectof two units since the units will work together in thex and y direction to move the boat lateral to return it to its desiredposition while they work in parallel directions to rotate the boat withsubstantially no lateral displacement. in addition, a fourth vector b isshown in PEG 4 which represents the biasing or anti-oscillation eiiectsupplied by the turn buclde arrangement described above. The vectorresolving unit resolves the vectors as shown in FIGURE 4 and suppliestwo vectors R and R related to the ma tude of the thrust required of thestern and bow pro ulsion units and the direction of thrust for the sternand bow propulsion units. The vector resolving unit in PlGURE 3 suppliesthe magnitude of this vector by means of the displacement type actuator1% while it supplies a direction of the thrust by displacing the pickup7'? radially around the potential disk 7t).

From the above description, it is seen that the vector resolving unit ofFTGURE 3 purely resolves the vectors which are proportional to thedesired lateral displacement of the vessel and the rotationaldisplacement of the vessel. By purely resolving these vectors the unitprovides two resulting vectors which describe the magnitude of thethrust required of each propulsion unit as well as the direction ofthrust for each propulsion unit. While the system is described asapplied to two propulsion units it could, of course, be used with anynumber of propulsion units merely by utilizing additional potentialdisks and pickup arrangements. Likewise, the propulsion units could belocated anywhere on the vessel other than at the center of rotation ofthe vessel and the resolving unit would. still provide for the mostefilcient use of the thrust available from the propulsion units. Ofcourse, it would be necessary to adjust the signals supplied from theresolving unit to each of the propulsion units to correct for thediilerent distances between the propulsion units and the center ofrotation of the vessel.

While the above description has been related solely to the mechanicalvector resolving unit shown in FIGURE 3, it is readily apparent thatother means may be utilized for purely resolving the vectors. Forexample, a completely electrical analog could be constructed to replacethe mechanical system shown in FIGURE 3.

In an electrical analog, the bias or anti-oscillation vector [2 could beadded to the vector x for one propulsion unit and subtracted for theother propulsion unit from the vector by means of summing amplifiers andsimilarly, the rotational vector 1) could be added to the vector y forone propulsion unit and subtracted from the vector y for the otherpropulsion unit. The Cartesian coordinates represented by the vectors xand y, thus modified, could then be converted to the polar coordinatesor vector-s representing propulsion unit thrust magnitude and directionby means of electrical resolvers. The scalar magnitude of the resultantcould be used directly to control the propulsion unit thrust, and thedirection of the resultant could be compared electrically with thepropulsion unit direction by means of synchros and the diiference usedto redirect the propulsion unit.

Also, it can be appreciated from the above description that the controlsystem of this invention can utilize inputs other than the x and ydisplacement vectors and the compass heading vector shown in FIGURES 1and 2. For example, the system could use inputs from electronic locatingdevices, such as radar, loran or shoran equipment. Such inputs wouldindicate the displacement of the vessel from its desired location in theform of two vectors and a vector which would indicate the differencebetween the actual heading of the vessel and its desired.

area /ea heading. The vector resolving unit of FIGURE 3 would thenresolve these vectors to determine what corrective action should betaken with regard to the propulsion units. Similarly, one could merelyutilize an operator to visually observe the position of the vessel withrelation to its desired position or course or then move the manualcontrol handle 55 of FIGURE 2 in the direction required to return thevessel to its desired posit-ion or course. This type of manual operationwould be advantageous when it is desired to move a vessel along a narrowwaterway or maneuver a vessel in confined space.

Accordingly, while but a single embodiment of this invention has beendescribed in detail, it obviously is susceptible to many modificationsand changes within its broad spirit and scope. Thus, this inventionshould not be limited to the specific details described herein but onlyits broad spirit and scope.

We claim as our invention:

l. A marine vessel positioning system comprising: at least twopropulsion means located on said vessel at separate positions spacedfrom the center of rotation of said vessel, first control means coupledto each of said separate propulsion units for directing the thrusteffect of said propulsion units in a horizontal plane, second controlmeans coupled to each of said separate propulsion units to vary thethrust effect of said propulsion units; locating means disposed on thevessel for determining its actual location and heading relative to itsdesired location and heading; a third control means coupled to saidlocating means to determine the difference between the actual locationand heading of the vessel and the desired location and heading, saidthird control means generating control signals related to saiddifference; actuating means coupled to said third control means toactuate said first and second control means for positioning said firstand second control means in response to the control signals.

2. A system for maintaining a marine vessel over a desired positioncomprising: separate propulsion means located at the bow and stern ofthe vessel, each propulsion means having a first control means to varythe direction of its thrust and a second control means to vary themagnitude of its thrust; a first position detecting means disposed onsaid vessel for detecting the horizontal position of the vessel in twodirections at an angle to each other and for supplying analog signals ofsaid detected position; a second position detecting means for detectingthe heading of the vessel and supplying an analog signal of saiddetected heading; a controller means coupled to said first and seconddetecting means for comparing said analog deflection signals and saidanalog heading signal with signals representing desired values of thedeflection and heading signals, said controller means also being coupledto a vector resolving unit to determine the required thrust vector ofeach propulsion unit; said vector resolving unit providing outputsignals indicating the desired direction of the thrust of eachpropulsion unit and separate output signals representing the magnitudeof the thrust of each propulsion unit required to return the difierencebetween the actual values of said deflection and heading signals andtheir desired values to zero.

3. A system for maintaining a floating vessel over a desired location onthe ocean floor comprising: separate propulsion means located at the bowand the stern of said vessel, each propulsion means comprising apropeller driven by a variable torque motor means and a rotation meansfor rotating the thrust direction of each drive unit through 360 about avertical axis; first detector means disposed on a guide line anchored tothe said location on the ocean floor at one end and on the vessel at theother end, said detector means measuring the angle between said guideline and the vertical in two planes at an angle to each other andsupplying output signals proportional to each of said measured angles; asynchro unit coupled to each propulsion unit to determine the direc- Cirlltli tion of the thrust effect of each propulsion unit; a compass meanspositioned on said vessel to determine the geographical heading of thevessel; a control device comprising two spaccd disks formed ofconducting material with each dish being divided into halves by separateinsulating strips on each side of the center of said disk, one of saidinsulating strips being narrow and the other wide, a separate pick-upbeing of insufiicient width to bridge the wide insulating strip on oneside of the center of the disk but of sufi'icient width to bridge thenarrow insulating strip on the other side of the center of the disk;circuit means for applying an electrical potential to both halves ofeach disk; the synchro unit of one pro pulsion unit being coupled to asynchro-receiving unit disposed to rotate one of said disks, the synchrounit of the other propulsion unit being coupled to a synchroreceivingunit disposed to rotate the other of said disks; a first actuatorcoupled to the compass means and disposed to move the pick-ups of bothdisks in opposite directions in relation to the difference between theactual and desired headings; second and third actuators coupled to saidfirst detecting means and disposed to move said pick-ups in unison intwo directions at an angle to each other; the pick-up of one disk beingcoupled to the rotation means of the propulsion unit whose synchro unitis coupled to the synchro-receivcr of said one disk and the otherpick-up being coupled to the rotation means of the other propulsion unitwhereby said rotation means Will rotate the propulsion units to alignthe pick-ups of both disks with the wide insulating strips on each disk;and control means coupled to the variable thrust drive means of eachpropulsion unit and to the pick-up of each disk to generate a signal tocontrol said variable thrust drive means of each propulsion unit inproportion to the displacement of the pick-up from the center of thedisk.

4. A system for controlling the movement of a vessel comprising: atleast two propulsion units disposed on said vessel in a spacedrelationship and at locations spaced from the center of rotation of saidvessel; detecting means disposed on the vessel for determining thehorizontal posi tion of the vessel along two axes at an angle to eachother; compass means disposed on the vessel to determine the heading ofthe vessel; a first means for comparing the horizontal position of theVessel with the desired position and for converting the difference intotwo thrust vectors at an angle to each other; second means for comparingthe compass heading with the desired heading of the vessel andconverting the difierence into a rotational couple; said first andsecond means being coupled to a vector resolving unit, said vectorresolving unit resolving said vectors to obtain a separate thrust vectorfor each propulsion unit indicating the thrust and direction anywhere ina full circle to be supplied by each unit and said vector resolving unitbeing coupled to a control means disposed on each propulsion unitwhereby the thrust and the thrust direction of each propulsion unit iscontrolled to return the vessel to its desired position.

5. The system of claim 4 wherein the detecting means determines thetranslational displacement of the vessel in a direction parallel to thelongitudinal axis of the vessel and in a direction normal to thelongitudinal axis of the vessel.

6. The system of claim 5 wherein the vector resolving unit adds thetranslational thrust vectors for all propulsion units and subtracts therotational thrust vector from the sum of the translational thrustvectors for some propulsion units and adds the rotational thrust vectorto the sum of the translational thrust vectors for the remainingpropulsion units.

7. The system or" claim 4 in which a third means is coupled to thevector resolving unit to supply a differential anti-oscillation vectorto the vector resolving unit.

8. A method for controlling the position of a vessel comprising:measuring the horizontal position of the vessel along two axes at anangle to each other, comparing the measured vessel position along eachaxis With the desired vessel position along each axis and generatingposition correction components for each axis, the vector sum of saidcomponents representing the basic thrust and direction of thrustrequired of a plurality of propulsion units; measuring the heading ofthe vessel, comparing the measured vessel heading with the desiredvessel heading and generating heading correction Vector couplecomponents along said axes; adding scalarly for each axis said positioncorrection components to said heading correction couple components, thesign of the said heading correction components being chosen for saidaddition for each propulsion unit such that a minimum of interferencewill be caused between position correction and heading correction;resolving the sum of all axial components for each propulsion unit intoa polar vector representing the required thrust magnitude and directionfor that propulsion unit and controlling each propulsion unit to obtainthe said required thrust and direction.

9. A system for controlling the position of a vessel comprising:measurement means for determining the position of the vessel incoordinates with axes in a horizontal plane and at some angle with eachother; controller means for each of the two separate axes of saidcoordinates, each controller means having adjustable means for settingthe desired position value along each axis, and

for setting the gain and other controller actions, said controller meanscomparing the measured position value with the desired position valuealong each axis and providing a control output signal for each of theaxis being controlled necessary to restore any displacement from thedesired position value for that axis; vector resolving means to convertsaid axis control signals into a resulting polar vector representingthrust magnitude and direction required to restore the desired positionof the vessel and propulsion means capable of providing variable thrustin any required direction in a full horizontal circle and arranged andcontrolled to provide the thrust and direction represented by said polarvector.

10. The system of claim 9 in which vessel heading is measured and thevalue of that heading is supplied to a third controller havingadjustable means for setting the desired heading value and for settingthe gain and other controller actions, the output of said thirdcontroller providing a signal which is proportional to the rotationalcouple required to restore desired vessel heading, said third controllerbeing coupled to said vector resolving means, at least two propulsionunits, said vector resolving means resolving said rotational couple andsaid polar vector separately for each propulsion unit, at least two ofsaid propulsion units being disposed away from the vessels center ofrotation to provide said rotational couple and the rotational vectors ofsaid rotational couple being aligned normal to a line drawn .from eachpropulsion unit through the vessels center of rotation.

11. A method for controlling the movement of a vessel comprising:

determining the actual location and heading of the vessel relative tothe desired location and heading of the vessel; utilizing the determinedlocation and heading of the vessel to generate vectors representing fora plurality of propulsion units the rotational and translational thrustrequired to move the vessel to the desired position and heading;generating an anti-oscillation vector; vectorially resolving therotational, translational and anti-oscillation vectors to obtain apropulsion vector for each propulsion unit representing the requiredthrust and direction of thrust for the propulsion unit; and controllingthe propulsion units in response to said propulsion vectors to obtainthe required thrust and direction of thrust for each propulsion unit.

References Cited by the Examiner UNITED. STATES PATENTS 2,155,456 4/39Von den Steinen 24477 2,555,577 6/51 Deland.

2,650,046 8/53 Vanderlip 244-17.13 2,669,785 2/54 Rydzewski 33-126.52,816,723 12/57 Bleakney 244-77 2,873,075 2/59 Mooers et a1 24417.132,941,495 6/60 Goldman 115-35 2,987,027 6/61 Wanzer 114-122 2,998,2108/61 Carter 24417.13 X 3,010,214 11/61 Postlewaite 33215 MILTON BUCHLER,Primary Examiner.

ANDREW H. FARRELL, FERGUS S. MIDDLETON,

Examiners.

1. A MARINE VESSEL POSITIONING SYSTEM COMPRISING: AT LEAST TWOPROPULSION MEANS LOCATED ON SAID VESSEL AT SEPARATE POSITIONS SPACEDFROM THE CENTER OF ROTATION OF SAID VESSEL, FIRST CONTROL MEANS COUPLEDTO EACH OF SAID SEPARATE PROPULSION UNITS FOR DIRECTING THE THRUSTEFFECT OF SAID PROPULSION UNITS IN A HORIZONTAL PLANE, SECOND CONTROLMEANS COUPLED TO EACH OF SAID SEPARATE PROPULSION UNITS TO VARY THETHRUST EFFECT OF SAID PROPULSION UNITS; LOCATION MEANS DISPOSED ON THEVESSEL FOR DETERMINING ITS ACTUAL LOCATION AND HEADING RELATIVE TO ITSDESIRED LOCATION AND HEADING; A THIRD CONTROL MEANS COUPLED TO SAIDLOCATING MEANS TO DETERMINE THE DIFFERENCE BETWEEN THE ACTUAL LOCATIONAND HEADING OF THE VESSEL AND THE DESIRED LOCATION AND HEATING OF THEVESSEL MEANS GENERATING CONTROL SIGNALS RELATED TO SAID DIFFERENCE;ACTUATING MEANS COUPLED TO SAID THIRD CONTROL MEANS TO ACTUATE SAIDFIRST AND SECOND CONTROL MEANS FOR POSITIONING SAID FIRST AND SECONDCONTROL MEANS IN RESPONSE TO THE CONTROL SIGNALS.